Niki Lauda has said Mercedes must take "two steps" forward if they are to move ahead in the battle with Ferrari this season.
The Silver Arrows and the Scuderia have two victories apiece in the opening four races of the 2017 season; but, while Mercedes have a one-point lead in the Constructors' Championship, Sebastian Vettel has stretched his World Championship lead to 13 points following his second-place finish in Russia.
"Ferrari is clearly ahead," Lauda told the Austrian newspaper Krone.
"We need to analyse what exactly is not working and take the right steps for Barcelona.
"Because all the teams will bring updates, Ferrari will make a step forward, we have to make two and Red Bull needs to make three."
Lauda also elaborated on the problems that Mercedes need to rectify if they are to make progress this season.
He added: "We have too much weight in the car, we need to improve the aerodynamics, and above all we need to understand why the new Pirelli tyres do not work as they do on the Ferrari."